The Collaborative International Dictionary of English v.0.48:

Snag \Snag\, v. t. [imp. & p. p. Snagged; p. pr. & vb. n.
   Snagging.]
   1. To cut the snags or branches from, as the stem of a tree;
      to hew roughly. [Prov. Eng.] --Halliwell.
      [1913 Webster]

   2. To injure or destroy, as a steamboat or other vessel, by a
      snag, or projecting part of a sunken tree. [U. S.]
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Snag \Snag\, n. [Prov. E., n., a lump on a tree where a branch
   has been cut off; v., to cut off the twigs and small branches
   from a tree, of Celtic origin; cf. Gael. snaigh, snaidh, to
   cut down, to prune, to sharpen, p. p. snaighte, snaidhte, cut
   off, lopped, Ir. snaigh a hewing, cutting.]
   1. A stump or base of a branch that has been lopped off; a
      short branch, or a sharp or rough branch; a knot; a
      protuberance.
      [1913 Webster]

            The coat of arms
            Now on a naked snag in triumph borne. --Dryden.
      [1913 Webster]

   2. A tooth projecting beyond the rest; contemptuously, a
      broken or decayed tooth. --Prior.
      [1913 Webster]

   3. A tree, or a branch of a tree, fixed in the bottom of a
      river or other navigable water, and rising nearly or quite
      to the surface, by which boats are sometimes pierced and
      sunk.
      [1913 Webster]

   4. (Zool.) One of the secondary branches of an antler.
      [1913 Webster]
      [1913 Webster]

   Snag boat, a steamboat fitted with apparatus for removing
      snags and other obstructions in navigable streams. [U.S.]


   Snag tooth. Same as Snag, 2.
      [1913 Webster]

            How thy snag teeth stand orderly,
            Like stakes which strut by the water side. --J.
                                                  Cotgrave.
      [1913 Webster]

WordNet (r) 3.0 (2006):

snag
    n 1: a sharp protuberance
    2: a dead tree that is still standing, usually in an undisturbed
       forest; "a snag can provide food and a habitat for insects
       and birds"
    3: an opening made forcibly as by pulling apart; "there was a
       rip in his pants"; "she had snags in her stockings" [syn:
       rip, rent, snag, split, tear]
    4: an unforeseen obstacle [syn: hang-up, hitch, rub,
       snag]
    v 1: catch on a snag; "I snagged my stocking"
    2: get by acting quickly and smartly; "snag a bargain"
    3: hew jaggedly

Moby Thesaurus II by Grady Ward, 1.0:

156 Moby Thesaurus words for "snag":
   baby tooth, bag, bar, bicuspid, blemish, block, blockade,
   bottleneck, brake, bucktooth, bug, canine, catch, clog, cog, comb,
   complication, coral heads, cordon, crack, crag, crimp, crown, crux,
   curb, curtain, cuspid, cutter, deciduous tooth, defect, defection,
   deficiency, dent, denticle, denticulation, dentil, dentition,
   determent, deterrent, difficulty, dogtooth, drag, drawback, enmesh,
   ensnare, entangle, entrap, eyetooth, failing, failure, fang, fault,
   faute, flaw, foible, fore tooth, foul, frailty, gagtooth,
   gang tooth, gold tooth, grinder, hamper, hang-up, harpoon, harrow,
   hazard, hindrance, hitch, hold-up, hole, hook, hurdle, impediment,
   imperfection, inadequacy, incisor, infirmity, ironbound coast, jag,
   joker, kink, land, lasso, ledges, lee shore, little problem, mesh,
   milk tooth, molar, nail, net, noose, objection, obstacle,
   obstruction, obstructive, one small difficulty, peak, pecten, peg,
   permanent tooth, pinch, pitfall, pivot tooth, premolar, problem,
   projection, quicksands, rake, ratchet, rift, rip, rockbound coast,
   rocks, rope, rub, sack, sandbank, sandbar, sands, sawtooth,
   scrivello, shallows, shoals, shortcoming, snaggle, snaggletooth,
   snare, sniggle, something missing, spear, spire, sprocket, spur,
   steeple, stricture, stumbling block, stumbling stone, taint, take,
   tangle, tangle up with, tear, tooth, trap, traverse, tush, tusk,
   undercurrent, undertow, vulnerable place, weak link, weak point,
   weakness, wisdom tooth



The Free On-line Dictionary of Computing (30 December 2018):

bug
bugs
defect
snag

    An unwanted and unintended property of a
   program or piece of hardware, especially one that causes
   it to malfunction.  Antonym of feature.  E.g. "There's a bug
   in the editor: it writes things out backward."  The
   identification and removal of bugs in a program is called
   "debugging".

   Admiral Grace Hopper (an early computing pioneer better
   known for inventing COBOL) liked to tell a story in which a
   technician solved a glitch in the Harvard Mark II machine
   by pulling an actual insect out from between the contacts of
   one of its relays, and she subsequently promulgated bug in
   its hackish sense as a joke about the incident (though, as she
   was careful to admit, she was not there when it happened).
   For many years the logbook associated with the incident and
   the actual bug in question (a moth) sat in a display case at
   the Naval Surface Warfare Center (NSWC).  The entire story,
   with a picture of the logbook and the moth taped into it, is
   recorded in the "Annals of the History of Computing", Vol. 3,
   No. 3 (July 1981), pp. 285--286.

   The text of the log entry (from September 9, 1947), reads
   "1545 Relay #70 Panel F (moth) in relay.  First actual case of
   bug being found".  This wording establishes that the term was
   already in use at the time in its current specific sense - and
   Hopper herself reports that the term "bug" was regularly
   applied to problems in radar electronics during WWII.

   Indeed, the use of "bug" to mean an industrial defect was
   already established in Thomas Edison's time, and a more
   specific and rather modern use can be found in an electrical
   handbook from 1896 ("Hawkin's New Catechism of Electricity",
   Theo. Audel & Co.)  which says: "The term "bug" is used to a
   limited extent to designate any fault or trouble in the
   connections or working of electric apparatus."  It further
   notes that the term is "said to have originated in
   quadruplex telegraphy and have been transferred to all
   electric apparatus."

   The latter observation may explain a common folk etymology of
   the term; that it came from telephone company usage, in which
   "bugs in a telephone cable" were blamed for noisy lines.
   Though this derivation seems to be mistaken, it may well be a
   distorted memory of a joke first current among *telegraph*
   operators more than a century ago!

   Actually, use of "bug" in the general sense of a disruptive
   event goes back to Shakespeare!  In the first edition of
   Samuel Johnson's dictionary one meaning of "bug" is "A
   frightful object; a walking spectre"; this is traced to
   "bugbear", a Welsh term for a variety of mythological monster
   which (to complete the circle) has recently been reintroduced
   into the popular lexicon through fantasy role-playing games.

   In any case, in jargon the word almost never refers to
   insects.  Here is a plausible conversation that never actually
   happened:

   "There is a bug in this ant farm!"

   "What do you mean?  I don't see any ants in it."

   "That's the bug."

   [There has been a widespread myth that the original bug was
   moved to the Smithsonian, and an earlier version of this entry
   so asserted.  A correspondent who thought to check discovered
   that the bug was not there.  While investigating this in late
   1990, your editor discovered that the NSWC still had the bug,
   but had unsuccessfully tried to get the Smithsonian to accept
   it - and that the present curator of their History of
   American Technology Museum didn't know this and agreed that it
   would make a worthwhile exhibit.  It was moved to the
   Smithsonian in mid-1991, but due to space and money
   constraints has not yet been exhibited.  Thus, the process of
   investigating the original-computer-bug bug fixed it in an
   entirely unexpected way, by making the myth true!  - ESR]

   [Jargon File]

   (1999-06-29)